A similar thing happened to me last year. We were selling our house and had to purchase Indemnity insurance as we hadn't had planning permission or building regulations for converting the garage into a room. This was done at least 10 years before we sold, by a previous owner. Working in the business we knew that neither was actually required either but writing to the Council to confirm would have delayed the sale (which was already dragging on) by at least 6 weeks. Of course, we were only asked nearly at point of completion, not at the beginning, so in the end we paid. Roughly �100 i think. We were NOT happy.